The present invention concerns modular molds for making containers, and more particularly to modular molds for making a hot-fill bottle which allows height and volume adjustments without requiring metal modifications of the mold sections.
A container, such as a biaxially-oriented PET beverage bottle, may be adapted to receive a hot-fill product with a minimum of thermal shrinkage and distortion. However, the bottle making and filling processes include many parameters which affect the product volume in the finished container. Thus, the final fill volume can be a function of: the metal dimensions of the blow mold, the mold process time, the mold operating temperature, the preform/bottle material distribution, the bottle age and storage conditions prior to filling (e.g., time, temperature, etc.), the filling line speed, the product fill temperature, the product fill pressure, and the time spent between the filler, capper and spray cooler. Changing any one of these parameters may have a significant effect on the final product volume, which is strictly controlled on the minimum side in order to comply with government labeling requirements and on the maximum side to avoid the undue expense of overfilling with excess product.
It would be desirable, everytime a bottle making or filling process parameter is changed, to avoid machining new mold pieces in order to achieve the desired fill volume. In addition, it would be desirable to make custom bottles for different product lines without having to completely redesign the mold.
It is known to split a bottle-making mold above and below the vacuum panel section for making a bottle of the type described in U.S. Pat. No. 4,863,046 entitled "Hot Fill Container," which issued Sep. 5, 1989 to Collette et al. In the known mold, a removable shoulder section provides custom flexibility above the label panel, and a shim is provided for varying the height (and thus the volume of the bottle) of the lower glue land--a cylindrical section located below the vacuum panels and above the base and to which adhesive is applied for attaching the label. However, this creates a glue land imbalance (since the upper glue land is not similarly extended) which may hinder a smooth attachment of the label, and the allowable height of the shim is severely limited by this glue land imbalance as well as by the required height of the vacuum panels. Increasing the bottle height without a similar increase to the height of the vacuum panel results in excess bottle vacuum as the product cools (and contracts) and the risk of vacuum collapse. Thus, the volume and height adjustability with this known modular mold is quite limited.
It is an object of this invention to provide an improved modular mold which solves the foregoing problems.